NestJs: Modern ways to build APIs with Typescript and NestJs

A major part of software engineering is building components that not only have well-defined and consistent APIs, but are also reusable. Components that are capable of working on the data of today as well as the data of tomorrow will give you the most flexible capabilities for building up large software systems.

In languages like C# and Java, one of the main tools in the toolbox for creating reusable components is generics, that is, being able to create a component that can work over a variety of types rather than a single one. This allows users to consume these components and use their own types.

In this lecture, I will teach you how to install and setup typescript with Node.js

There are two main ways to get the TypeScript tools:

• Via npm (the Node.js package manager)

• By installing TypeScript’s Visual Studio plugins

• For NPM users:

  > npm install -g typescript

  
  

  You have to create the .ts file and run the tsc and typescript file

The primary reason you create a generic function is because you have some code that meets two criteria:

• It's a function or class that will work with a variety of data types

• The function or class uses that data type in several places

You have other options: When you have code that works with a variety of data types, you could write one version of the function for each data type, but that's a lot of work and a maintenance nightmare. You could also write one function and have it use the any keyword for its data types, but that would mean abandoning type safety.

Provided that the data types involved are used in several places in your code, a generic function or class is a better solution than your other options: generic functions let you write one version of your code and ensure that the code consistently uses data types (and then, of course, let the developer specify the data type when calling the function/instantiating the class).

In the above example, the type variable T is specified with the function in the angle brackets getArray<T>. The type variable T is also used to specify the type of the arguments and the return value. This means that the data type which will be specified at the time of a function call, will also be the data type of the arguments and of the return value.

In this lecture I will teach how you can create generic function to accept multiple type variables. You can also create a generic function with multiple Type variables

In this lecture, I will teach you how to restrict the generic function to specified type.

In this lecture you will learn how to define interfaces to define the object properties and function type

In this lecture, I will teach you how to create Interface to describe the function type

Each kind of decorator requires a different function signature, as the decorator is provided with different parameters depending on the decorator use. This section will provide several practical examples that can be used as a starting point for your own decorators.

You can make a decorator configurable by converting your decorator function into a decorator factory. A decorator factory is a function that returns a decorator function. The factory can have any number of parameters that can be used in the creation of the decorator.

In this video, we are going to learn about property decorator. A property decorator can only be used to observe that a property of a specific name has been declared for a class. Property decorators ignore any return, underscoring their inability to affect the decorated properties

In this video, you are going to learn about Parameter decorator. A parameter decorator can only be used to observe that a parameter has been declared on a method.

In this lecture, you are going to learn about class decorator. It allows programmers to modify the behaviour of function or class.Decorators allow us to wrap another function in order to extend the behaviour of the wrapped function, without permanently modifying it.

In this video, I will teach you what are you going to build in this section. We will build basic CRUD functionalities with Array.

In this video, I will teach you how to create a POST endpoint to save record in Array. I will teach you how to inject the service into controller by using dependency injection pattern

In this video, I will teach you how to get request payload using DTO. A DTO is an object that defines how the data will be sent over the network. We could determine the DTO schema by using TypeScript interfaces, or by simple classes. Interestingly, we recommend using classes here

In this video, we will create a find all endpoint to fetch all the records. You will also learn how to implement delete endpoint to delete all the records

Pipes have two typical use cases:

• transformation: transform input data to the desired output

• validation: evaluate input data and if valid, simply pass it through unchanged; otherwise, throw an exception when the data is incorrect

In this video, we are going to validate request payload using built-in ValidationPipe. We will define decorator based validations in DTO object.

In this video, we will review the source code of ValidationPipe. I will show you how ValidationPipe works in under the hood. How ValidationPipe uses class-validator and class-transformer package

Middleware is a function which is called before the route handler. Middleware functions have access to the request and response objects, and the next() middleware function in the application’s request-response cycle. The next middleware function is commonly denoted by a variable named next.

In this video, you are going to learn how to create a custom logging middleware in NestJs. You are going to learn middlewares works in Nestjs

While the base (built-in) exception filter can automatically handle many cases for you, you may want full control over the exceptions layer. For example, you may want to add logging or use a different JSON schema based on some dynamic factors. Exception filters are designed for exactly this purpose.

In this video, I will teach you what are interceptors and why do we need them. An interceptor is a class annotated with the @Injectable() decorator. Interceptors should implement the NestInterceptor interface.

In this video, I will show you how to map the response before sending to the client. We will create a custom interceptor to map the response

In this lesson, I will teach you how to install Mysql server on your machine. You will also learn how to install Mysql workbench on your machine

In this video, we will create an Entity in NestJs Project. Entity is a class that maps to a database table (or collection when using MongoDB). You can create an entity by defining a new class and mark it with @Entity():

In this video, I will teach you how to save new record in new record in MySQL database table using TypeORM repository API. TypeORM Repository provides CRUD functions , we are going to use these functions

In this video, I will teach you how to find, update and delete products from Mysql database. I will show you how to use TypeORM repository to implement these methods

One-to-one is a relation where A contains only one instance of B, and B contains only one instance of A. Let's take for example User and Profile entities. User can have only a single profile, and a single profile is owned by only a single user.

In this video, I will show you how to perform Create, Update, Delete, and Find the records with one to one relation. You will learn how to add data in relation entities

Many-to-one / one-to-many is a relation where A contains multiple instances of B, but B contains only one instance of A. Let's take for example User and Photo entities. User can have multiple photos, but each photo is owned by only one single user.

In this video, I will teach you how to implement many to many relationship. Many-to-many is a relation where A contains multiple instances of B, and B contain multiple instances of A. Let's take for example Question and Category entities. Question can have multiple categories, and each category can have multiple questions.

In this lecture, You will learn how to install MongoDB on your machine

In this video, I will teach you how to connect NestJs application with MongoDB using Mongoose package.

In this lecture, I will teach you what is Authentication and why Authentication is important. I will also teach you the basics of JSON Web Token authentication. How Json Web Token Authentication works

Passport is authentication middleware for Node.js. Extremely flexible and modular, Passport can be unobtrusively dropped in to any Express-based web application. A comprehensive set of strategies support authentication using a username and password, Facebook, Twitter,

In this video, You are going to learn how to authenticate user using Passport JWT Strategy in NestJs application. A Passport strategy for authenticating with a JSON Web Token. This module lets you authenticate endpoints using a JSON web token. ... secretOrKey is a string or buffer containing the secret (symmetric) or PEM-encoded public key (asymmetric) for verifying the token's signature.